Method of making aluminum soaps



United States Patent 07 3,244,735 METHGD OF MAKING ALUMINUM SOAPS Neil Ross Artman, Greenhills, Ohio, ass'ignoi' to The Procter & Gamble Company,-Cincinnati, Ohio, a corporation of Ohio No Drawing. Filed Dec. 31, 1962, Ser. No. 248,306

8 Claims. (Cl. 260-414) the corresponding acids being of the formula RCOOH, R being an alkyl ranging from 2 to 30 carbon atoms.

In the prior art (USP. 2,827,458, Mirviss'etal.) it is disclosed that aluminum soaps (aluminum salts) having alkyl chain lengths from 2 to 29 carbon atoms in each alkyl group can be made by reacting an aluminum trialkyl with canbon dioxide under heat and pressure preferably in the presence of a diluent such as C -C paraffin, or aromatics such as benzene, toluene'or thelike. The yield of aluminum soaps obtained by this method (as measured by the amount of free organic carboxylic acid formed by the subsequent hydrolysis and/or acidification of the soap) in general, is considerably less than the theoreticalobtainable value, being on the order of .1020% of thevalue which theoretically could be realized by the process high percentage of the theoreticallyobtainable value of the soap. It is a further object of'thi's invention to pro vide an improved method of making aluminum soaps which is more economical than those known in the art. These aluminum soaps are especially useful as'inte'rm'ediates in the preparation of carboxylic acids by'hydrolyzing and/or acidifying the soaps.

Other objects'of the invention will be apparent from the following description.

It has been found, in accordance with the process of this invention that aluminum salts of organic 'carboxyl-ic acids (aluminum soaps) can be prepared in ahigh percentageyield of the theoretically obtainable value by the interaction, under temperature and pressure, of analminum trialkyl with excess carbon dioxide in the presence of'a solvent which forms a complex with'the aluminum trialkyl, the solvent-complexer being selected from the group consisting of ethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, isopropyl ether, dibutyl ether, and

tetrahydropyran.

3,244,735 Patented Apr. 5, 1966 "ice In the practice of this invention, the aluminum trialkyl starting compound has the general formula of:

R -Al Where each-of the Rs is the same or a different alkyl radical and contains from 2 to 30 carbon atoms. These compounds are formed in a manner described hereinafter. When admixed with the ether solvent-complexers used herein, the aluminum trialkyls form a complex with the ether which can be represented as follows (ethyl ether isused as an example):

This aluminum trialkyl-ether complex in turn is reacted, under certain forcing conditions (time, temperature and pressure) with excess carbon dioxide, the molar ratio of carbon dioxide to alkyl aluminum being at least 3 to 1, and preferably 10:1 or higher. The product of this carbonation reaction is an aluminum soap and the reaction can be illustrated as follows (ethyl ether is used as an example):

The aluminum soap can be separated from the etheraluminum soap mixture formed by the reaction ofEquation 3 and recovered from solution. is to heat the mixture of aluminum soap, ether, by-product hydrocarbons, and unreacted materials to drive oif all of the undesired materials which are volatile, thereby leaving the non-volatile aluminum soaps behind. Passing a stream of steam or inert gas such as nitrogen through the solution of reaction products will also aid in stripping outthe volatile materials. Another method of recovering the aluminum soaps in the form of a useful product is to add to the reaction mixture a material which, although volatile, is less volatile than the materials to be removed. This mixture can then be" heated at atmospheric or reduced pressure to drive off all of the volatile undesired materials and that partof the added high-boiling material which co-distil-ls with the undesired materials, leaving a solution or'suspension of aluminum soaps in the desired, high boiling material. rial can be lubricatingioil, in which case the final product is thickened grease.

Aluminum soaps are useful in the manufacture of lubricating oils'and greases, and as 'flattingagents, waterproofing agents, and grinding aids. They are also useful asintermediates and can be hydrolyzed and/ or acidified to form the corresponding'carboxylic acids which are useful in the manufacture of a large variety of organic compounds-includingwater-soluble detergent compounds as those skilled'in'the'art' are well aware.

As stated herein, the use of the ether solvent-complexers in the carbonation of aluminum trialkyls to form aluminum soaps results in a significantly higher percentage A preferred method Such additive high-boiling mate yield of aluminum soap, as compared to the theoretical yield, than is achieved by other means taught in the art. While this invention is in no way to be limited by an explanation of the cause of the high yields, the following is submitted as a hypothesis.

Ethers form complexes with aluminum trialkyls of the type indicated in Equation 3 above. Toward at least some reagents, such aluminum trialkyl-ether complexes are less reactive than are uncomplexed aluminum trialkyls. In view of this, it is speculated that the presence of the aluminum trialkyl as an ether complex during the course of the carbonation reaction (Equation 3) rather than as the free aluminum trialkyl, prevents a subsequent reaction between the first formed product of the reaction, namely aluminum soap, and remaining uncarbonated aluminum trialkyl. If the reaction between unreacted aluminum trialkyl and aluminum soap were allowed to take place, owing to the omission of the ether solvent-complexer, the products of the reaction would be hydrocarbons and tertiary alcohols; insofar as aluminum trialkyl would be consumed in the reaction between aluminum soap and unreacted aluminum trialkyls, it would in like measure be unavailable for the formation of further quantities of aluminum soap.

The starting aluminum trialkyls used in the process of this invention can be derived from any suitable source. Lower aluminum trialkyls are available commercially. One method of preparing higher molecular weight aluminum trialkyls is by growing ethylene onto low molecular weight aluminum trialkyls or aluminum alkyl hydrides in a manner represented by the following reaction wherein ethylene is grown onto aluminum tripropyl.

x, y, and z represent integers ranging from 1-28 and averaging between about 8-14 and n is an integer greater than 3. I,

Instead of aluminum tripropyl in the above reaction, other low molecular weight aluminum alkyls which can be used include, for example, aluminum triethyl, aluminum tributyl, aluminum diethyl hydride, and aluminum ethyldihydride. The above method of preparation is described in German Patent No. 917,006, and U.S.P. No. 2,827,458, granted March 18, 1958.

Another method of preparation of higher aluminum trialkyls is to form the aluminum trialkyls by a displacement reaction wherein an unsaturated alkyl compound (olefin) is reacted with a low molecular weight aluminum trialkyl, such as tri-iso-butyl aluminum, according to the following equation:

R in the above formula is an alkyl group which can range from about 2 to about 24 carbon atoms. Suitable unsaturated alkyl compounds include, for example, l-octene, l-nonene, l-decene, l-undecene, l-dodecene, I-tetradecene, l-pentadecene, l-hexadecene, l-heptadecene and l-octadecene. It is essential to have thedouble bond in the 1-position.

Where the aluminum soap formed by the process of this invention is to be used directly or indirectly in the manufacture of detergents it is preferred that alkyl groups in the aluminum trialkyl range from about 9 to about 17 carbon atoms in chain length, since carboxylic acids formed by acidification of aluminum soaps are most useful for making detergents when the carbon chain length is from about to about 18 carbon atoms.

The displacement method of making aluminum trialkyls is preferable to the ethylene build-up method if the aluminum soap formed by the carbonation of the aluminum trialkyl is to be used as a precursor for organic monocarboxylic acids for detergent manufacture since it is easier to control the chain length of the alkyl groups by the former method. When the aluminum trialkyl is formed by the ethylene build-up type reaction, the chain lengths of the alkyl groups formed vary over a wide range.

In a preferred aspect of this invention, the aluminum soaps formed by the process described herein are hydrolyzed and/ or acidified by methods known to those skilled in the art to form the corresponding organic carboxylic acids as illustrated thuslyz ll 2R(J0Na H2SO4 2Ro-0H Nansoi) The aluminum trialkyl compounds which can be used in the present process of this invention can contain branched or normal alkyl radicals. It is preferred, however, to employ aluminum compounds containing the straight chain or normal alkyl substituents. Accordingly, the employment of straight chain aluminum trialkyl compounds will, when carrying out the instant process, result in a production of straight chain aluminum soaps which can either be used as lubricants, for example, or can be used to produce straight chain organic monocarboxylic acids which are useful in producing detergent compounds. Examples of aluminum trialkyls which can be used in the process of this invention are aluminum triethyl, aluminum tripropyl, aluminum tributyl, aluminum trihexyl, aluminum trioctyl, aluminum trinonyl, aluminum tridodecyl, aluminum triundecyl, aluminum tritetradecyl, aluminum tri(tridecyl) and higher molecular weight aluminum tri-alkyls. Some examples of mixed aluminum trialkyls which can be employed are aluminum monoethyl dipropyl, aluminum dibutyl monooctyl, aluminum didecyl monooctyl, aluminum dihexadecyl monodecyl, aluminum dipropyl monobutyl, aluminum dioctyl monoisohexyl, aluminum ditetradecyl monohexadecyl, aluminum di(isododecyl) monohexadecyl, aluminum di(isotetradecyl) monohexadecyl, aluminum dihexadecyl monoethyl, aluminum di(isohexadecyl) monododecyl, aluminum ditetradecyl monododecyl, and the like. A preferred aluminum trialkyl starting compound for use in this invention is aluminum triundecyl.

The following is a detailed description of the process of this invention including processing conditions which are required to give the high yield of aluminum soaps obtainable by the process described herein.

In the practice of this invention, the aluminum trialkyl (liquid) and ether solvent-complexer in the desired mole ratio of solvent to aluminum trialkyl (as described below) are placed in a reaction vessel and the vessel is sealed. While the practice of this invention is not limited to any particular type of reaction vessel, it has been found that a standard glass-lined autoclave is eminently suitable as the reaction vessel for the process described herein. After the autoclave is sealed and while still cold, a molar excess (at least 3 moles carbon dioxide to 1 mole aluminum trialkyl) of carbon dioxide is added, then heat is applied. Though less convenient it would also be possible to heat the aluminum tri-alkyl ether complex in the autoclave and then add CO from a cylinder. The pressure is maintained in the range of from about 500 p.s.i.g. to about 20,000 p.s.i.g. and the temperature in the range of from about C. to about 250 C. The reaction is con- 5 tinued under these conditions for a period of from about 1 to about 60 hours.

The preferred pressure is about 5000 p.s.i.g. when the temperature is maintained at a level of about 200 C. If the pressure is lower than about 800 p.s.i.g. the yield falls off considerably although it is still at a significantly increased level over that obtained using prior art processes. Thus the preferred pressure range is from 800 p.s.i.g. .to 5000 p.s.i.g. The temperature of the reaction is quite important. Highest yields are obtained when the temperature of the reaction mixture is maintained at about 170'-.200 thus this isv the preferredv temperature range. Higher temperatures diminish theyield somewhat while lower temperatures diminish the yield greatly. The time of the reaction will, of course,.depend'on the particular aluminum trialkyl'compound used, the pressure and the temperature. The shorter the reaction time, the less is the yield of aluminum soap because of incomplete carbonation reaction. The preferred reaction time is about 20 to 30 hours.

It is important in the practice of this invention that the proper mole ratio of aluminum trialkyl to the ether solvent-complexer be used. It has been found that a mole ratio of lessthan' about-111' results'in a low yield of aluminum soaps due to side reactions. Ratios ranging from about 1:1 to-about' 1:10 or higher give optimum results. The preferred mole ratio is 1 mole of aluminum trialkyl to about 25 moles of etherl The ether solvent-complexer usedin this reaction is very important. It'has'been found that by using-an ether solVent-complexer of theclassmentioned supra, very high yields-of aluminum SOap can be-obtained'as-compared to-the methods disclosed'in the prior art (SEQCX- planation above). The ethers used herein act not only as complexers of the aluminum trialkyl but they also act as solvent for the reactants and for the" reaction products of the process. This complexing-solvent action aids in the completion of the reaction and in obtaining high yields. The preferred ether for use in the process of this invention is ethyl ether.

It is essential to the practice of this invention in order to-get complete carbonation of the aluminum trialkyl compounds that excess carbon dioxide be present in the reaction vessel. The carbon dioxide is added to the reac tion vessel before or afterheat is applied in the form of a gas at cylinder pressure. Higher carbon dioxide pres sures can be achieved bypacking'the-free' space 'of the reaction vessel with Dry Ice (solid CO before sealing it and then pressuring in CO at cylinder pressure into the still cold vehicle. It is desirable to agitate the reaction vessel during the period of the reaction.

As stated before, the aluminum soaps formed by the process of this invention can be used when separated from the other reaction products as themselves or they can be hydrolyzed and/or acidified to ultimately form the monocarboxylic acids useful in the production of organic compounds such as detergents. Methods of hydrolysis and/or acidification of aluminum soaps to carboxylic acids are outlined above.

The following examples are illustrative, but not limitative, of the practice of this invention.

EXAMPLE I 20 ml. (.04 mole) of tridodecylaluminum was cautiously mixed with 5 ml. (.09 mole) of ethyl ether in a 300 ml. glass lined autoclave. The free space in the autoclave was packed with Dry Ice before sealing. After sealing, and before the application of heat, CO gas was let into the autoclave at cylinder pressure, then heat was applied in the usual manner by means of an electric heating coil. In this example the temperature was maintained at 200 C. and the pressure inside the reaction vessel was 1600 p.s.i.g. The reactants were agitated for 20 hours. The heating coil was then shut off and the autoclave was 6 allowed to cool to room temperature, then the pressure was released. The solution containing the aluminum soaprether mixture, unneacted starting materials, and byproducts of the reaction, was then hydrolyzed by treatment with aqueous sodium hydroxide whereupon two phases were formed, the top layer containing the unre-' acted diluents, by-products, and oil-soluble compounds and the bottom layer containing the sodium salt of tri-- decanoic acid. The two layers were then separated and the sodium salt was then acidified with dilute sulfuric acid again forming two layers, the top layer containing the fatty acid and the bottom layer containing H O, Na SO and H The fatty acid was then separated. As the amount'oforganic carboxylic acidformed is directly proportional to the amount of aluminum soap formed by the carbonation reaction, it canread-ily be seen that the percentage yield of monocarboxylic acid as compared to theoretical obtainable value is the same as the percentage yield of aluminum soap as compared to the theoretical obtainable value. The percent aluminum soap, aluminum tridecanoate, formed as compared to the theoretically obtainable value inthisexample was 53%. The aluminum tridecanoate is useful as a lubricant; or, as was seen above, it can be acidified'with H 50 to form tridecanoic acid which in turn can be saponified with caustic soda to form a detergent compound. The acid can also be sulfonated with S0 to form a different type of detergent compound.

Instead of hydrolyzing and/ or acidifying the aluminum soap formed in the carbonation reaction above to recover monocarboxylic acids, it is also possible to separate the aluminum soap as a pure compound by driving oif the volatile materials with heat, and recovering the residual aluminum soap. The soap can then be used as lubricating aids, grinding aids or for other purposes herein mentioncd.

In the above reaction the ethyl ether can be replaced by tetrahydrofuran or dioxane with comparable results. In addition, the tridodecyl aluminum can be replaced with tributyl aluminum trioctyl aluminum, tritetradecyl aluminum, or tridecyl aluminum, for example, and comparable results are obtained'thereby.

EXAMPLE II 20 ml. of tridodecylaluminum was mixed'slowly with 5 ml. of tetrahydrofuran in a 300 ml. glass lined autoclave. After thorough mixing, Dry Ice was packed into the vacant space and then the autoclave was sealed. Prior the application of heat excess CO was let into the autoclave at cylinder pressure and then heat was applied by means of an electric heating coil. The mixture was reacted with constant agitation for a period of 20 hours at a pressure of 5600 p.s.i.g. and at a temperature of 210 C. At the end of 20 hours the heating coil was shut off and the autoclave allowed to cool to room temperature, then the pressure was released. The solution containing the aluminum soaps was treated with sodium hydroxide and C monocarboxylic acid ultimately formed from the soaps by means of the hydrolysis and acidification process of Example I. The percent of yield compared to that which was theoretically possible was 42%.

EXAMPLE III In this example, tridodecyl altuninum was reacted with carbon dioxide in the presence of ethyl ether in an autoclave identical to the one used in Examples I and II under the conditions indicated in Table I. The percent yield of aluminum tridecanoate was measured by gravimetric analysis of the corresponding carboxylic acid (tridecanoic acid) produced by the subsequent acidification of the aluminum tridecanoate. (Same procedure as in Example I.)

Table I Tridodecyl- Ethyl 002 Temp., Time, Yield, aluminum ml. ether, pressure, 0. Hrs. percent p.s.i.g.

Thus it can be seen from the above table and the other examples given that the percentage yield of aluminum soaps obtained in the carbonation of aluminum trialkyls by using the ether solvent-complexers described herein is significantly greater than the 10-20% yields obtainable following the process described in the prior art Without the presence of the ethers disclosed herein. Such a result was surprising and unexpected.

What is claimed is:

1. In the process for the preparation of aluminum soaps the improvement which comprises reacting an aluminum trialkyl, the alkyl groups ranging from 9 to 17 carbons, with excess carbon dioxide in the presence of 1 mole to 10 moles, based on the number of moles of aluminum trialkyl undergoing reaction, of a solvent which forms a complex with the aluminum trialkyl, said solvent being selected from the group consisting of ethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, isopropyl ether, dibutyl ether, and the tetrahydropyran, for a period of 1 hour to 60 hours at a temperature in the range of 150 C. to 250 C., and at a pressure in the range of from 500 p.s.i.g. to 20,000 p.s.i.g.

2. The process of claim 1 in which the aluminum trialkyl is tridodecylaluminum.

3. The process of claim 1 in which the ether is tetrahydrofuran.

4. The process of claim 1 in which the alkyl groups in the aluminum trialkyl. starting compounds are identical and are 11 carbon atoms in length.

5. In the process for the preparation of aluminum soaps the improvement which comprises the interaction of an aluminum trialkyl having from 9 to 17 carbon atoms in each alkyl chain with excess carbon dioxide in the presence of about 1 mole to 10 moles, based on the number of moles of aluminum trialkyl undergoing reaction, of ethyl ether which forms a complex with aluminum trialkyl for a period from 1 hour to hours at a temperature in the range of from C. to 250 C. while maintaining a pressure in the reaction zone .in the range of 500 p.s.i.g. to 20,000 p.s.i.g.

6. In the process of preparing alkyl aluminum soaps the improvement which comprises reacting an aluminum trialkyl having the following formula:

a wherein each R represents an alkyl radical containing from 9 to 17 carbon atoms with excess carbon dioxide in the presence of 1 mole to 10 moles based on the number of moles of aluminum trialkyl undergoing reaction of a solvent which forms a complex with the aluminum trialkyl, said solvent being selected from the group consisting of ethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, isopropyl ether, dibutyl ether, and

References Cited by the Examiner UNITED STATES PATENTS 1,990,320 2,827,458 3/1958 Mirviss et a1. 260414 XR CHARLES B. PARKER, Primary Examiner.

IRVING MARCUS, Examiner.

2/1935 Fulweiler et al. 260-414 XR? 

1. IN THE PROCESS FOR THE PREPARATION OF ALUMINUM SOAPS THE IMPROVEMENT WHICH COMPRISES REACTING AN ALUMINUM TRIALKYL, THE ALKYL GROUPS RANGING FROM 9 TO 17 CARBONS, WITH EXCESS CARBON DIOXIDE IN THE PRESENCE OF 1 MOLE TO 10 MOLES, BASED ON THE NUMBER OF MOLES OF ALUMINUM TRIALKYL UNDERGOING REACTION, OF A SOLVENT WHICH FORMS A COMPLEX WITH THE ALUMINUM TRIALKYL, SAID SOLVENT BEING SELECTED FROM THE GROUP CONSISTING OF ETHYL ETHER, TETRAHYDROFURAN, DIOXANE, ETHYLENE GLYCOL DIMETHYL ETHER, ISOPROPYL ETHER, DIBUTYL ETHER, AND THE TETRAHYDROPYRAN, FOR A PERIOD OF 1 HOUR TO 60 HOURS AT A TEMPERATURE IN THE RANGE OF 150*C. TO 250*C., AND AT A PRESSURE IN THE RANGE OF FROM 500 P.S.I.G. TO 20,000 P.S.I.G. 